Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 9 of 9

Thread: High chlorine in pool

  1. Back To Top    #1

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    High chlorine in pool

    Hi All.

    I've just bought a house with a 7,000L outdoor swim spa (about 1800 gal for you guys across the Pacific)
    It was filled up and had been running before we moved in, except that it was shut down for two weeks because the heater element failed and they/we were waiting for a replacement). It runs of a SWG.

    The element was replaced the other day, we've brought it up to temp, and I brought a test kit.

    The chlorine test (DPD) goes clear as soon as the tablet starts to dissolve (a slight pink during the dissolving) which from what I read previously can be due to high chlorine. The local pool store tested with the same result.

    As my wife is keen to get in, I bought some Sodium thiosulphate to bring the levels down and turned off the swg. I've added 300g in stages, which by the calculation on the pack should drop the level by 42ppm. It still bleaches out the test.

    If I dilute it down to about 1/5 with tap water, it reads around 5 (max on the test chart).

    There are also some pool-check test strips the previous owner left that I believe are a tetramethylbenzidine test. It should go from clear to a dark blue. It goes a dark brown, which I assume means it's still way over.

    There's not a lot of sunlight at this time of year and it's pretty cold.

    What's the best option?
    Leave the cover off throug the day?
    Run the blower to aerate it and drive more Cl out?
    More sodium thiosulphate?

    TIA

  2. Back To Top    #2


    TFP Guide

    cowboycasey's Avatar
    Join Date
    Jul 2013
    Location
    Fletcher, OK
    Posts
    3,346

    Re: High chlorine in pool

    Hey there

    Ok, there is a test kit that is exactly like we use here and will help you very much, you have 2 options.. Yes they are expensive there but way worth it...

    1. Buy just the FAS-DPD test kit to test up to 50ppm chlorine so your know exactly what you're dealing with. Chlorine FAS-DPD 3-in-1 Kit Clear Choice Labs

    2. a complete test kit, this option only if your test kit does not have everything already Total Pool Water Testing Kit, Salt Water Clear Choice Labs

    The sun will take the chlorine down but how long is unknown so leaving the cover off will help.. I have never used sodium thiosulphate so I am unsure on its use...

    I hope this helps
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
    links: pool school * Recommended-Levels * SLAM * CYA chart * Test kits * How To Post Pictures * Poolmath * OCLT ** Support your website if we helped you :) **

  3. Back To Top    #3

    Join Date
    May 2016
    Location
    Ste-Anne-des-Lacs, Quebec, Canada
    Posts
    30

    Re: High chlorine in pool

    You can try Vitamin C (ascorbic acid). We have used this once and it works great. Try it in a sample that you have tinted for the FC test, crush a vitamin c and drop some into the sample to confirm your vitamin C works. My husband crushed 250g of vitamin C in a blender and dropped it in the skimmer. He then tested the water coming out of the return in the pool, there was no chlorine in that water. Unfortunately, I do not have a recipe about how much vitamin C is required. The good thing about this is that vitamin C is fairly cheap and easy to come by.

    Above ground pool 15' x 24' oval, 48" deep at average level => 9300 gallons/ 35200 liters
    Hayward sand(glass beads) filter, Hayward 1.5hp 2-speed pump
    WSP wood-burning heater and Nirvana F1000 heat pump

  4. Back To Top    #4

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    Re: High chlorine in pool

    Thanks for the input and suggestions

  5. Back To Top    #5

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    Re: High chlorine in pool

    At least I've figured out how the chlorine got so high.
    Looking at the way it's configured, when the temp is low the filter pump kicks in, as the heater runs inline with this. The SWG also runs whenever this pump runs - contrary to the manual they left, the SWG doesn't have a timer. So when the heater failed the pump and SWG would have been running continuously due to the low temp. It also would have run continuously while were heating it back up.
    The previous owners weren't up with all the technical side, so probably didn't realize.

  6. Back To Top    #6

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    Re: High chlorine in pool

    As a follow up on this one, I calculate that my FC must have been over 100!
    I took a few measures to bring it down quick, as there was a slight leak in two pumps and I wasn't sure if the high chlorine was damaging the seals or other components.

    So I:
    - Added the full 400g container of sodium thiosulfate (Should drop FC by 61ppm according to pack, 32 by other calculations)
    - Left cover off through daylight hours for a week (should have dropped it a bit)
    - Added 1.2 L of 3% H2O2 (should drop 11.5 ppm)
    My Clear Choice Labs test kit then arrived, and FC tested as somewhere around 50 still (transition was very slow so hard to be exact)!
    Bought a 1L bottle of 595g/L H2O2, did a quick calculation, and added 250 ml in two steps (should drop by about 47 ppm).

    Tested a couple of hours later and the pool was at 4 ppm

    Pump seals now replaced, and all is running well.
    1,800g AG Endless Swim Spa, Cartridge Filter, Davey Pumps, Davey Ecosalt MES13AMP SWG
    6kW electric heater. Installed 2013, I became owner May 2016

  7. Back To Top    #7

    Join Date
    Aug 2014
    Location
    Northern IL
    Posts
    4,615

    Re: High chlorine in pool

    Yikes. Good luck and keep us up to date!

  8. Back To Top    #8
    needsajet's Avatar
    Join Date
    Jan 2016
    Location
    Sydney, NSW, Australia
    Posts
    3,552

    Re: High chlorine in pool

    By any chance, is there a dial under a sliding cover on the front of the SWG controller, marked 0-100? or Min-Max? If so, that's % of time the SWC will run when turned on.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

  9. Back To Top    #9

    Join Date
    May 2016
    Location
    Hobart, Tasmania, Australia
    Posts
    13

    Re: High chlorine in pool

    Quote Originally Posted by needsajet View Post
    By any chance, is there a dial under a sliding cover on the front of the SWG controller, marked 0-100? ...
    Yep - turned it to zero when I first tested the chlorine. Since I got the level down to 4 I've been adjusting it, and I think somewhere around 15% should hold the level constant through winter with the spa cover mainly on, apart from when in use.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •